Merge pull request #6 from StratoDem/5-error-messages

5 error messages

.gitignore

@@ -17,3 +17,4 @@ pip-selfcheck.json
 *.egg-info/
 *.whl
 venv/
+dist/

CHANGELOG.md

@@ -0,0 +1,50 @@
+# CHANGELOG
+
+## 1.2.0 - 2018-05-15
+### Changed
+- Improves clarity of error messages for large component comparisons
+  ##### Old logic:
+  raise `AssertionError` with large string difference between JSON objects if the component did not match the snapshot, which led to difficult to read error message like:
+  ```
+  AssertionError: {'pro[136 chars]en': 'another one'}, 'namespace': 'dash_html_c[77 chars]Div'} != {'pro[136 chars]en': [1, 2, 3]}, 'namespace': 'dash_html_compo[73 chars]Div'}
+  ```
+  ##### New logic:
+  raise `AssertionError` with large string difference between JSON objects if the component does not match the snapshot, **and**
+  add new details section about the **first local mismatch** between the component and snapshot:
+  ```
+  DETAILS:
+
+  <class 'list'> != <class 'str'>
+  CONTEXT 1:
+
+  {"children": [1, 2, 3]}
+
+  CONTEXT 2:
+
+  {"children": "another one"}
+  ```
+  or
+  ```
+  DETAILS:
+
+  P != Span
+  CONTEXT 1:
+
+  {"type": "P", "props": {"children": "another one"}, "namespace": "dash_html_components"}
+
+  CONTEXT 2:
+
+  {"type": "Span", "props": {"children": "another one"}, "namespace": "dash_html_components"}
+  ```
+
+## 1.1.0 - 2018-04-11
+### Added
+- This package now checks for an environment variable (UPDATE_DASH_SNAPSHOTS) and will automatically overwrite snapshots if it is set to TRUE
+
+## 1.0.1 - 2018-03-27
+### Added
+- MIT License
+
+## 1.0.0 - 2018-03-27
+### Added
+- Initial publication

setup.py

@@ -13,7 +13,7 @@
 
 setup(
     name='dash-snapshot-testing',
-    version='1.1.0',
+    version='1.2.0',
     author='Michael Clawar, Eric Linden',
     author_email='tech@stratodem.com',
     packages=['snapshot_test'],

snapshot_test/__tests__/__snapshots_2__/MyOtherUnitTestCase-my-test-unique-id.json

@@ -0,0 +1 @@
+{"namespace": "dash_html_components", "type": "Div", "props": {"children": [{"namespace": "dash_html_components", "type": "P", "props": {"children": "wow"}}, {"namespace": "dash_html_components", "type": "Span", "props": {"children": "another one"}}], "id": "test-id"}}

snapshot_test/__tests__/__snapshots__/MyUnitTestCase-my-test-unique-id.json

@@ -0,0 +1 @@
+{"namespace": "dash_html_components", "type": "Div", "props": {"children": [{"namespace": "dash_html_components", "type": "P", "props": {"children": "wow!"}}, {"namespace": "dash_html_components", "type": "Span", "props": {"children": "this works"}}], "id": "test-id"}}

snapshot_test/__tests__/test_snapshot_test_case.py

@@ -29,3 +29,23 @@ def test_component(self):
         my_component = html.Div([html.P('wow'), html.Span('another one')], id='test-id')
 
         self.assertSnapshotEqual(my_component, 'my-test-unique-id')
+
+    def test_component_2(self):
+        my_component = html.Div([html.P('wow'), html.P('another one')], id='test-id')
+
+        self.assertRaises(
+            AssertionError,
+            lambda: self.assertSnapshotEqual(my_component, 'my-test-unique-id'))
+
+    def test_component_3(self):
+        my_component = html.Div([html.P('wow'), html.Span([1, 2, 3])], id='test-id')
+
+        self.assertRaises(
+            AssertionError,
+            lambda: self.assertSnapshotEqual(my_component, 'my-test-unique-id'))
+
+        my_component = html.Div([html.P('wow'), html.Span((1, 2, 3))], id='test-id')
+
+        self.assertRaises(
+            AssertionError,
+            lambda: self.assertSnapshotEqual(my_component, 'my-test-unique-id'))

snapshot_test/snapshot_test_case.py

@@ -13,13 +13,18 @@
 import os
 import plotly.utils
 import unittest
+from typing import Any
 
 from dash.development.base_component import Component
 
 
 __all__ = ['DashSnapshotTestCase']
 
 
+class DashSnapshotMismatch(Exception):
+    pass
+
+
 class DashSnapshotTestCase(unittest.TestCase):
     snapshots_dir = None
 
@@ -60,7 +65,21 @@ def assertSnapshotEqual(self, component: Component, file_id: str) -> None:
                 # Load a dumped JSON for the passed-in component, to ensure matches standard format
                 expected_dict = json.loads(
                     json.dumps(component_json, cls=plotly.utils.PlotlyJSONEncoder))
-                self.assertEqual(self.__load_snapshot(filename=filename), expected_dict)
+                existing_snapshot = self.__load_snapshot(filename=filename)
+                try:
+                    self.__check_object_equality(
+                        expected_dict,
+                        existing_snapshot,
+                        context1=expected_dict,
+                        context2=existing_snapshot)
+                except DashSnapshotMismatch as e:
+                    self.assertEqual(
+                        existing_snapshot,
+                        expected_dict,
+                        '\n\nDETAILS:\n\n{}'.format(e))
+                self.assertEqual(
+                    existing_snapshot,
+                    expected_dict)
         else:
             # Component did not already exist, so we'll write to the file
             with open(filename, 'w') as file:
@@ -127,3 +146,55 @@ def __get_snapshots_dir(cls) -> str:
                 os.mkdir(cls.snapshots_dir)
 
             return cls.snapshots_dir
+
+    @classmethod
+    def __check_object_equality(cls, obj1: Any, obj2: Any, context1: Any, context2: Any) -> None:
+        if type(obj1) != type(obj2):
+            raise DashSnapshotMismatch(
+                '{} != {} {}'.format(
+                    type(obj1),
+                    type(obj2),
+                    cls.__create_error_context(context1, context2)))
+        elif isinstance(obj1, (list, tuple)):
+            if len(obj1) != len(obj2):
+                raise DashSnapshotMismatch(
+                    'Length of object 1 ({}) does not match object 2 ({}) {}'.format(
+                        len(obj1),
+                        len(obj2),
+                        cls.__create_error_context(obj1, obj2)))
+            else:
+                for obj1_element, obj2_element in zip(obj1, obj2):
+                    cls.__check_object_equality(
+                        obj1=obj1_element,
+                        obj2=obj2_element,
+                        context1=obj1,
+                        context2=obj2)
+        elif isinstance(obj1, dict):
+            if set(obj1.keys()) != set(obj2.keys()):
+                raise DashSnapshotMismatch(
+                    'Keys do not match ({} vs {}) {}'.format(
+                        obj1.keys(),
+                        obj2.keys(),
+                        cls.__create_error_context(context1, context2)))
+            else:
+                for k1 in obj1.keys():
+                    cls.__check_object_equality(
+                        obj1=obj1[k1],
+                        obj2=obj2[k1],
+                        context1=obj1,
+                        context2=obj2)
+        elif isinstance(obj1, (str, int, float)):
+            if obj1 != obj2:
+                raise DashSnapshotMismatch(
+                    '{} != {} {}'.format(
+                        obj1,
+                        obj2,
+                        cls.__create_error_context(context1, context2)))
+        else:
+            raise TypeError('DashSnapshotTesting does not support type {}'.format(type(obj1)))
+
+    @staticmethod
+    def __create_error_context(context1: Any, context2: Any) -> str:
+        return '\nCONTEXT 1:\n\n{}\n\nCONTEXT 2: \n\n{}'.format(
+                    json.dumps(context1),
+                    json.dumps(context2))